National Instruments 370753C-01 Manual De Usuario

You can choose to scale the system output here for zero steady-state error 
in the step response. This is accomplished in an intuitive manner, dividing 
the system 

sys_cl

 by the desired scaling factor.

sys_cl = sys_cl/51.76;

v_obc = step(sys_cl, 0:.1:10);

plot (v_obc, {xlab = "Time", ylab = "Magnitude"})

In Figure 1-9 the step response shows zero-steady-state error, little 
overshoot, and a response time of less than seven seconds.

Figure 1-9.  Step Response for Observer-Based Design

The system response is quite good, implying that your state estimates were 
satisfactory. You can do some further simulation, this time returning all the 
states directly from the original plant, and get a graphical picture of how the 
estimates track the actual states. First, you need to create the closed-loop 
system with all states available.

The 

abcd( )

 function extracts the A, B, C, and D matrices from a system 

object. When you call it here, all you are interested in is the closed-loop 
A matrix, so you do not need to extract the other state-space matrices.

A_cl = abcd(sys_cl);